The proposed research project aims at studying four biologically significant enzymes in prostaglandin metabolism. 15- Hydroxyprostaglandin dehydrogenase and prostaglandin A isomerase control the biological inactivation of prostaglandins, while prostaglandin E 9- keto reductase and prostaglandin E dehydrase regulate the interconversion of functionally different prostaglandins. These four enzymes will be isolated from respective sources of mammalian tissues. Affinity chromatography with appropriate ligands attached to Sepharose will be used to facilitate purification of enzymes in addition to conventional fractionation and chromatographic techniques. Various physical parameters and chemical properties of these enzymes will be studied by established techniques. Kinetic mechanism with respect to the order of addition of substrate will be elucidated from initial velocity, product inhibition, dead end inhibition and alternate substrate studies. Regulation of enzyme activity by various positive and negative modulators will be demonstrated by endogenous modulators, other possible physiological modulators and various types of drugs. The mechanism of action of these modulators will be studied by steady state enzyme kinetics, binding studied, fluorescence quenching and other physicochemical methods. The research program will provide an understanding of the basic properties of the enzymes, the nature and the mechanism of action of those factors involved in regulating the biological activity of prostaglandins. Moreover, it will give valuable information to the similar studies in various organs and further stimulate investigations on the role of prostaglandins in various physiological systems.